The appearance of Zika virus, an RNA virus being transmitted in Brazil by mosquitoes, but originally imported from Africa, has raised some old chestnuts about public health.
The disease resembles dengue somewhat, and is usually a mild illness transmitted to tissues through various lymphatic cells. But it might lead to encephalitis, or particularly to severe brain birth defects in newborns, so the main danger would be to pregnant women.
The New York Times has a big story by Simon Romero.
But Wikipedia also notes that it is possible that Zika might be sexually transmitted. That raises a dangerous idea from the 1980s that the right wing sometimes tried to make about AIDS and HIV, that sexual (male homosexual) activity could amplify it, and then, for all we knew, insects might pick it up and transmit it to the general population. That didn’t happen. But the gay paper, Charles Ortleb’s “The New York Native” floated a theory in the early 1980s (before HTLV-III was fully accepted) that an arbovirus, African Swine Fever, could be involved, and that the USDA was doing experiments with it in a secret facility on Long Island.
Update: Jan. 28, 2016
The Washington Post has a 70-second "what you need to know" video here. The virus apparently does cause brain damage in the unborn child, and this seems to have happened numerous times in Brazil. One country is encouraging women not to have children until 2018. The virus is spread only by mosquitoes. It is likely to cause no or mild symptoms in healthy adults. It might be possible for it to spread by mosquito from one infected person to another, so you can imagine the public health "morality" scenarios about wearing long pants and long sleeves near infested areas. So far there are few cases in the US, none acquired here.
Update: Feb. 3, 2016
A case of sexual transmission has been reported in Dallas (BBC story). Blood donors who have traveled in infested areas or believe they could have been exposed are asked to self-defer for 28 days.